In-situ surfactant and chemical oxidant flushing for complete remediation of contaminants and methods of using same

ABSTRACT

The present invention relates to the removal of subsurface contaminants and methods of using same. In more particular, but not by way of limitation, the present invention relates to an integrated method for remediating subsurface contaminants through the use of a low concentration surfactant solution (and methods of making and using novel surfactant solutions) followed by an abiotic polishing process to thereafter achieve a substantially reduced subsurface contaminant concentration that surfactant flushing alone cannot achieve. The present invention is focused on remediation of high viscosity hydrocarbons, such as heating oils or coal tars, with a combination of pre-injection of bio-co-solvent and surfactant (and polymer) flush approach.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Ser. No. 11/054,582,filed Feb. 9, 2005; which is a continuation of U.S. Ser. No. 10/290,424,filed Nov. 6, 2002, now U.S. Pat. No. 6,913,419; which claims thebenefit under 35 U.S.C. § 119(e) of U.S. Provisional Application Ser.No. 60/333,244, filed Nov. 11, 2001, entitled “USE OF IN-SITU SEQUENTAND CHEMICAL OXIDANT FLUSHING FOR COMPLETE REMEDIATION OF CONTAMINATEDSOILS AND GROUNDWATERS”, the contents of which are expresslyincorporated herein in their entirety by reference.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates to the removal of subsurface contaminantsand methods of using same, and more particularly, but not by way oflimitation, the presently claimed and disclosed invention(s) relate toan integrated method for remediating subsurface contaminants through theuse of a low concentration surfactant solution (and methods of makingand using novel surfactant solutions) followed by an abiotic polishingprocess to thereafter achieve a substantially reduced subsurfacecontaminant concentration that surfactant flushing alone cannot achieve.Additionally, the surfactant solution alone can be used to achieve asubstantially reduced subsurface contaminant concentration. Finally, thepresently claimed and disclosed invention(s) include the use of abiodegradable co-solvent capable of substantially reducing subsurfacecontaminants having a viscosity of from 50-1500 cp and/or a low aqueoussolubility.

2. Background Information Relating to the Invention

Surfactant enhanced subsurface remediation (SESR) is a unique technologyfor expediting subsurface remediation of non-aqueous phase liquids(NAPLs). Studies known to those in the art have previously evaluated theSESR technology in both laboratory scale studies and field scaledemonstration studies. Traditionally, the surfactant system in SESR(typically an anionic or nonionic surfactant), is designed to removeorganic contaminants (including chlorinated solvents) from contaminatedsoil. Surfactant systems significantly increase the solubility ofhydrophobic organic compounds and, if properly designed and controlled,also significantly increase the mobility of NAPLS. A significantlyreduced remediation time thereby results, as well as increased removalefficiency (up to 3 or 4 orders of magnitude) and reduced cost of NAPLremoval through use of surfactant system for subsurface remediation.

Surfactant flushing solutions, typically, can be designed to beeffective under most subsurface conditions. In most cases, theeffectiveness of the surfactant flushing solutions is not reduced due tothe presence of more than one contaminant. Naturally-occurring divalentcations and salts may affect the performance of certain surfactants, aswell as the removal efficiency for cationic heavy metals. It ispossible, however, to design an effective surfactant system for removalof the target contaminants under any of these conditions. A number offactors influence the overall performance and cost effectiveness of SESRsystems. These factors include: local ground water chemistry; soilchemistry (e.g. sorption, precipitation); ability to deliver thesurfactant solution to the area of contamination; surfactant effects onbiodegradation of the. NAPL compounds as well as degradation of thesurfactants; public and regulatory acceptance; cost of the surfactant;recycle and reuse of the surfactant, if necessary; and treatment anddisposal of waste streams. Bench scale tests (treatability studies) mustbe conducted on site specific soils and NAPL (if available) to ensurethe optimal system is selected for a particular site.

Surfactant flushing can remove a large portion of the mass of subsurfacecontaminant liquid. In general, it is not expected that surfactantflushing alone will have a high probability of reducing the subsurfacecontaminant concentration to a level necessary to allow the site to beconsidered “remediated.” Therefore, a treatment train (or integrated)approach is necessary to speed up or achieve the closure of the site. Itis to such an integrated approach involving a pre-selected surfactantsolution flush coupled with an abiotic oxidation polishing step andmethods thereof that the presently disclosed and claimed invention(s) isdirected.

Typically, the viscosities of contaminants or NAPLs are between one toten centipoises (cp, or 10⁻² g cm⁻¹sec⁻¹) and, in some occasions, theymay reach tens up to one hundred centipoises. Prior art (crude) oilrecovery industries that used surfactant flushing for removal of highlyviscous oils would generally apply a polymer solution (or so called“polymer drive”) in order to increase the sweep efficiency and oilrecovery from the porous media and/or soils. Other generally knownmethods involve the addition of heat to reduce the oil viscosity, or theinjection of foam in order to gain better mobility control to achievehigher oil recovery.

Such generally known methods are limited with respect to recoveringsignificant amounts of complex viscous liquid contaminants, such as coaltars (commonly found at former manufactured gas plants), heating oils,bunker oils, creosotes (used as wood preservatives), polychlorinatedbiphenyls (PCBs), dioxins, and motor oils. Some of these complex wasteoils might contain tens to hundreds of different compounds.Unfortunately, these complex wastes found at contaminated sites couldalso sometimes reach viscosities of from 50 to 1500 cp. In addition tothese high viscosities, the low aqueous solubility of these complexorganic fluids also poses a significant challenge for any attempt toremediate the impacted soil and groundwater.

Therefore, an improved surfactant flushing system is herein claimed anddisclosed that is capable of substantially reducing the subsurfacecontamination of complex viscous NAPLs.

SUMMARY OF THE PRESENT INVENTION

The present invention is directed to a method for substantially removingsubsurface contaminants through an integrated approach utilizing apre-selected surfactant solution and a pre-selected chemical oxidant.Such an innovative integrated approach satisfies a need in themarketplace for a cost-effective and less time consuming system toremove substantially all subsurface contaminants—a level of remediationthat has been traditionally unavailable. A method of the presentinvention comprises the steps of introducing an effective amount of atleast one pre-selected surfactant solution and an effective amount of atleast one pre-selected chemical oxidant. The combination of thepre-selected surfactant solution and the pre-selected chemical oxidantare capable of substantially removing subsurface contaminants.Additionally, the surfactant solution alone can be used to achieve asubstantially reduced subsurface contaminant concentration. Finally, thepresently claimed and disclosed invention(s) include the use of abiodegradable co-solvent capable of substantially reducing subsurfacecontaminants having a viscosity of from 50-1500 cp and/or a low aqueoussolubility, which will be difficult to remove using the patentedsurfactant system-alone as documented in the previous claim.

The presently claimed and disclosed invention(s) also relate to asubsurface contaminated site that is substantially remediated by thisintegrated approach and novel surfactant solutions.

DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic diagram showing, generally, an integratedsurfactant flushing and treatment system according to the presentinvention.

FIG. 2 is a graphical representation showing the results of a NAPLremoval test in a one-dimensional (1-D) column.

FIG. 3 is a schematic representation of pre- and post-surfactant freephase gasoline distribution in a “Shallow Zone” at an undergroundstorage tank contamination site—i.e. Carroll's Grocery in Golden, Okla.

FIG. 4 is a schematic representation of pre- and post-surfactantflushing/chemical oxidation benzene concentration distributionmethodology of the present invention in a “Shallow Zone” at anunderground storage tank contamination site—i.e. Carroll's Grocery inGolden, Okla.

FIG. 5 is a graphical representation showing the results of a TCEbreakthrough test with sequent surfactant and chemical oxidationflushing in a 1-D column.

DETAILED DESCRIPTION OF INVENTION

It is to be understood that the invention is not limited in itsapplication to the details of construction and the arrangements of thecomponents set forth in the following description (e.g. texts, examples,data and/or tables) or illustrated or shown in the drawings. Theinvention is capable of other embodiments or of being practiced orcarried out in various ways. Also, it is to be understood that thephraseology and terminology employed herein is for purpose ofdescription and should not be regarded as limiting and one of ordinaryskill in the art, given the present specification, would be capable ofmaking and using the presently claimed and disclosed invention in abroad and non-limiting manner.

As used herein, the term “subsurface contaminant” refers to any organicor inorganic impurity or halogenated solvent (such as a chlorinatedsolvent) that is toxic to the underground surface. Additionally, theterm “surfactant solution” refers to any anionic or nonionic surfactantor co-surfactant combination that is functionally capable of removingorganic or inorganic contaminants as well as halogenated solvents (suchas a chlorinated solvent) from a contaminated subsurface area, such assubsurface soil or water systems. Further, the term “oxidant” refers toany oxidizing agent capable of degrading a contaminated plume orentrapped residual pollutants whether they are organic, inorganic, orhalogenated solvents. The term “polishing step” as used herein, refersto the innovative abiotic process of the presently disclosed and claimedinvention that includes the steps of injecting or introducingpredetermined concentrations of a chemical oxidant to further degradeand reduce the subsurface contaminant subsequent to a surfactantflushing step. “Integrated approach” as used herein, refers to a lowconcentration surfactant flush in combination with the abiotic polishingstep. “Remediation” as used herein, refers to the substantially completeremoval of soil and groundwater pollutants by various treatments orrestoring methods to achieve the standard set by the responsibleregulatory agency for the particular contaminated subsurface system(e.g. National Primary Drinking Water Regulations (NPDWR) for subsurfaceground water).

Due to certain advantages associated with the use of the integratedapproach of the presently claimed and disclosed invention, one ofordinary skill in the art will most likely recognize the benefits ofthis approach when time is of the essence. One such advantage is that byusing the low concentration surfactant flush step in combination withthe subsequent abiotic polishing step, a higher probability exists ofreducing the subsurface contaminant concentration to a level necessaryto allow the site to be considered remediated—i.e. substantially allcontaminants have been removed. This process will tend to achieveminimal pollutant content of the underground surface while decreasingthe time spent as compared to prior art techniques that utilize a higherconcentration surfactant flush as the sole means of remediating acontaminated site.

Prior to the inventive concept of the present invention, higherconcentration surfactant flushing alone has been the common method ofsite remediation. As shown in FIG. 1, the present invention includes anoverall integrated surfactant flushing and treatment system 10. Apre-determined surfactant solution 20 is prepared in a mixing tank 30.After the surfactant solution 20 is prepared, the surfactant-NAPL phasebehavior is evaluated on-site. If the surfactant solution 20 meets allcriteria set for the surfactant—NAPL phase behavior, such as optimalmicroemulsion (either Winsor Type III or Type I), the surfactantsolution 20 is delivered to a targeted treatment zone 40 via aninjection well 50 and a pumping system 60. Removed contaminant andsurfactant solution 70 is extracted from a recovery well 80. Thefree-phase oil is separated from a surfactant stream in an oil/waterseparator 90. If the contaminant and surfactant solution 70 is pHsensitive for its recovery, a pH-adjustment tank 100 could be addedbefore the oil/water separator 90 to reduce the solution pH and enhancethe surfactant separation. From the oil/water separator 90, a wastestream 110 is sent to an air stripper 120 or other equipment (such asliquid-liquid extraction) to remove dissolved volatile organic chemicals(VOC) 130. The waste stream 110 is delivered to a pre-filtration system140 to remove the large solid particle or sediment in the waste stream110. If surfactant reuse is required, the waste stream 110 will gothrough a second pH-adjustment tank 150 and an ultrafiltration membranesystem 160. Most surfactant micelle phase will be rejected at theretentate side 170 and sent back to the mixing tank 30 for reuse. Thewaste water containing mainly surfactant monomer and trace contaminantwill pass through the ultrafiltration membrane system 160 for finaldisposal 180 or sent to a wastewater treatment plant for treatment.

As outlined and shown in particular examples hereinafter, the presentlyclaimed and disclosed methodology of the present invention demonstratessignificant removal of NAPL from a contaminated source area viaremediation. In one embodiment of this invention, surfactant flushingprojects were conducted at a surfactant concentration ranging between 3to 8 wt % of surfactant based upon the total weight of the surfactantsolution (e.g. 3 wt % would be 3% surfactant/97% water or othersolvent). This range may be somewhat over-conservative because, withinthis range of surfactant concentrations, reuse or reconcentration of therecovered surfactant typically is necessary to improve the economics ofthe overall project. In order to recover/separate the surfactant,contaminant concentrations must be reduced to acceptable levels in thesurfactant solution and then the surfactant must be re-concentrated forreinjection. In other embodiments of this invention, surfactantconcentrations in a range from about, 0.05% to about 15 wt % arecontemplated for use. In a most preferred embodiment of this invention,a lower surfactant concentration, such as 0.1%, is most desirable.Several advantages of using a low surfactant concentration, are: (1)significant savings on chemical use and project cost; (2) minimizingand/or completely eliminating the reuse and recycling of the recoveredsurfactant; and (3) improving the above-ground treatment efficiency(e.g., less retention time for breaking the macro- or microemulsionduring the oil/water separation stage, and less foaming of surfactant).Therefore, the ability of lowering the costs of a SESR project, such aswith utilizing a lower surfactant concentration, further improves thetotal cost effectiveness for the remediation of sites. The quantity ofsurfactant necessary for use with the presently disclosed and claimedinvention is up to one order of magnitude (from several weight percentsreduced to several thousands ppm or mg/L) less than prior art surfactantflushing systems used for light non-aqueous phase liquids (LNAPLs) aswell as for dense non-aqueous phase liquids (DNAPLs).

The surfactant solution of the presently claimed and disclosed inventionmay be any anionic, cationic, or nonionic surfactant or any combinationsthereof as well as one or more combinations thereof. These combinationsinclude, but are not limited to: anionic surfactant/anionic surfactant;anionic surfactant/nonionic surfactant; anionic surfactant/cationicsurfactant; nonionic surfactant/nonionic surfactant; and nonionicsurfactant/cationic surfactant combinations, to name but a few of thepossible permutations.

Further, the present invention encompasses an abiotic process to addressthe post-surfactant polishing step to further enhance site remediation.This abiotic process involves injecting pre-determined concentrations ofchemical oxidant to degrade the dilute contaminant plume and/or traceentrapped residual pollutant(s) that remain after the surfactantflushing step. The effectiveness of these oxidants depends on the typesof contaminants and geological formations found at the site. Thus, thechemical oxidant is chosen or “predetermined” based on an analysis ofthe site: i.e. the functionality of the chemical oxidant must match orbe capable of degrading any remaining contaminants or pollutants. Thus,one of ordinary skill in the art, given the present specification, wouldbe capable of selecting an appropriate chemical oxidant given anidentification of the contaminants or pollutants to be remediated.

The two most common oxidizing agents used for in-situ chemical oxidationare hydrogen peroxide and potassium permanganate, yet various otheroxidizing agents including, but not limited to, sodium permanganate,ozone, chlorine dioxide, or dissolved oxygen may be used. In thechemical oxidation process known as Fenton's reaction, injection ofhydrogen peroxide is typically combined with an iron catalyst underreduced pH conditions to generate powerful hydroxyl free radicals (OH⁻).Since 1934, Fenton's reagent has been recognized as an effective meansfor destroying organic compounds in wastewater and most recently as anin-situ treatment method for soil and groundwater. The dissolved ironacts as a catalyst for generating the hydroxyl radical, resulting infree-radical oxidation of the contaminant. A low pH is necessary to keepthe iron in the ferrous state. While the reaction can be performedsuccessfully at a pH range between 5 and 7 (using a so-called modifiedFenton's Reagent and processes), the performance improves at even lowerpH values (as low as 2 to 3). Obtaining optimal subsurface pH conditionsis often limited by the soil buffering capacity, which is site-specific.For example, if naturally-occurring carbonates in the soil are high, asignificant acid dose is required to reduce the pH at the site andthereby improve the performance of the oxidizing agent.

Potassium permanganate oxidation creates little heat or gas, thereforecontaminant treatment occurs primarily through oxidation. Potassiumpermanganate is an oxidizing agent with a unique affinity for organiccompounds containing carbon-carbon double bonds, aldehyde groups orhydroxyl groups. Under normal subsurface pH and temperature conditions,the primary oxidation reaction for perchloroethylene (PCE) andtrichloroethylene (TCE) involves spontaneous cleavage of thecarbon-carbon bond. Once this double bond is broken, the highly unstablecarbonyl groups are immediately converted to carbon dioxide througheither hydrolysis or further oxidation by the permanganate ion.Selection of the proper oxidant is based on several factors including,but not limited to, contaminant characteristics, site geochemicalconditions, soil buffering conditions of site, and etc. Fenton's reagentis capable of oxidizing a wide range of compounds while potassiumpermanganate is more selective and is best suited for chlorinated ethenecontaminants such as PCE and TCE. Potassium permanganate often providesmore rapid destruction of specific compounds when compared to Fenton'sreagent, however.

Previous prior art results from field tests raised concerns on theeffectiveness of using chemical oxidation for contaminated source zoneremediation. Mainly, this was due to the high concentration of oxidantrequired, the large amount of heat and gas released in the subsurface,and the formation of solid-precipitate at the surface of the contaminantliquid pool. Utilizing the presently disclosed and claimed methodology,however, the bulk of the contaminant has been previously removed bysurfactant flushing, followed by a very low concentration (preferablyless than 1.0 wt %) of oxidant which can be used. The amount of heatgenerated and the volume of gas released ceases to be a limiting factor.Using the methodology of the presently claimed and disclosed invention,surfactant flushing followed by chemical oxidation is highly effectivefor contaminant remediation. Thus, neither surfactant flushing norchemical oxidation alone can accomplish substantially, one hundredpercent remediation of a contaminated site. The combination ofsurfactant flushing followed by chemical oxidation does, however, resultin a substantially remediated site that had been contaminated prior totreatment. The presently disclosed and claimed methodology greatlyreduces the long-term risk and financial burden of the owner of thecontaminated site in a site closure program versus a maintenance-likeapproach such as pump-and-treat. The uniqueness of the presently claimedand disclosed integrated process approach provides significantimprovement on the NAPL clean-up efficiency as compared to thestand-alone surfactant flushing and stand alone in situ chemicaloxidation for site remediation.

Experiment Methodology

Surfactant Selection and System Design. Selection of the propersurfactant system utilizing a series of laboratory screening tests isone of the most crucial steps in conducting a successful surfactantflushing project. Laboratory surfactant screening typically consists ofthe following tests: contaminant solubilization tests, surfactant-NAPLphase behavior properties tests, surfactant sorption and precipitationtests, and contaminant extraction-column studies. Representativeprocedures of these tests are briefly described below. One of ordinaryskill in the art, however, would appreciate the significance and stepsnecessary to conduct such tests given the present specification. Thepurpose of these tests is to select the best surfactant system forapplication at the site—the surfactant is optimized for both thephysical and chemical conditions of the site and the contaminant.

Contaminant solubilization of NAPL Solubilization tests are used todetermine the solubilization capacity of the surfactant systems (seee.g. Shiau et al., 1994; Rouse et al. 1993). For a DNAPL contaminant,the objective of the solubilization test is to select a surfactantsystem with ultra-solubilization potential without mobilizing the NAPL.For a LNAPL contaminant, the optimal surfactant system is chosen basedon mobilization of NAPL under the ultra-low interfacial tensioncondition. Typically, surfactant systems under such conditions willproduce a so-called Winsor Type III (or the middle phase) microemulsionvia testing of surfactant-NAPL phase behavior properties (Shiau et al.,1994). The solubilization capacity of site-specific NAPL is determinedfor the surfactants by two methods: direct visual observation (see Shiauet al., 1994) and gas chromatography/flame ionization detector (GC/FID)(i.e., EPA Method 8015 for gasoline range organics (GRO), diesel rangeorganics (DRO), and other volatile organic chemicals (VOCs)) and/or gaschromatography/photoionization detector (GC/PID) measurement (i.e., EPAMethod 8021B for BTEX compounds). Direct visual observation is used as apreliminary screening tool for various surfactant and NAPL systems. Whena proper surfactant/co-surfactant system is utilized, a middle-phasemicroemulsion (a translucent liquid phase intermediate between the waterand NAPL phases) is observed in a mixture of surfactant and NAPL system.

Surfactant-NAPL phase behavior properties. The difference between amicroemulsion and macroemulsion (or emulsion) is that a microemulsion isthermodynamically stable while a macroemulsion is thermodynamicallyunstable and will ultimately separate into oil and water phases.Typically, a macroemulsion of NAPL and surfactant mixture appears opaqueafter equilibration. During the surfactant-NAPL phase behavior testing,equal volume of NAPL and surfactant solution is added to a batch reactor(at capacity between 10 mL to 40 mL) and the system is adjusted withsalt (NaCl), hardness (CaCl₂), or co-solvent (short chain alcohols) tochange the hydrophobicity, a crucial parameter to achieve the optimalsurfactant phase behavior, of NAPL and surfactant mixture. The solutionis shaken and left to equilibrate at room temperature (18° C.) followinga 24-hour pre-mixing period. Formation of a stable middle-phasemicroemulsion becomes complete within a few hours to one day. Thepresence of a middle-phase microemulsion is confirmed by visualobservation (formation of a translucent liquid) and instrumentation(measuring the ultra-low interfacial tension (IFT) with a spinning droptensiometer). (See Cayias et. al, 1975; Shiau et. al, 2000).

Sorption, Precipitation, and Phase Behavior Analyses. These tests assessthe potential for surfactant losses under subsurface conditions (seeShiau et al., 1995 for details). Surfactants can be lost due tosorption, precipitation, and adverse phase behavior reactions. Excesssurfactant sorbed or precipitated onto soil inhibits systemeffectiveness and increases costs. Sorption testing quantifies theamount of surfactant lost to soil and facilitates a surfactantcomparison analysis. Some surfactants may precipitate or phase separatedue to the presence of salts, divalent cations or temperaturefluctuations. It is essential to ensure that the surfactant will notprecipitate under site specific aquifer conditions. Surfactant loss dueto precipitation and/or phase separation not only hinders performancebut also plugs the aquifer. Formation of an opaque solution in a mixtureof NAPL/surfactant indicates an adverse phase behavior, which does notprovide a satisfactory sweep efficiency and/or solubilization capacityin the subsurface.

Contaminant Extraction-Column Studies. One-dimensional (1-D) columntests are conducted to simulate flow through conditions in the aquifer(see Shiau, et al., 2000 for detailed procedures). Although it isdifficult to simulate actual site conditions, valuable information canbe obtained from column studies. This information includessolubilization enhancement under continuous flow conditions and headlosses during flushing through the media.

The results of the column studies aid in the design of pilot andpotential full-scale application designs of the presently claimed anddisclosed inventive methodology. Column test results are used toquantify the number of pore volumes (PV) required to mitigate the NAPLfor each surfactant system and the polishing step. Previous laboratoryand field studies indicate that the solubilization mechanism requires3-15 PV for most NAPL mass recovery (Shiau, et al. 2000). For themobilization mechanism, the required surfactant solution flush isbetween one to two pore volumes (PV) to recover the majority of the NAPLmass. From site soil-packed columns, residual saturation is achieved inthe column by adding the site-specific contaminant(s) to the column(between 0.01 to 0.2 PV) followed by water to remove excess contaminant.A mass balance of NAPL is determined to estimate the residualconcentration.

Under low surfactant concentration conditions (<1 wt % of surfactant),reuse and recycling of surfactant is economically unnecessary forfull-scale implementation. Addition of bio-degradable co-solvent to thepre-selected surfactant solution for highly viscous contaminants asclaimed and disclosed in this invention will increase the costs ofchemical use and the remediation project. Therefore, recycledbio-co-solvent might be necessary to save the chemical and remediationcosts. New processes may be developed for the recycling and reuse of thebio-degradable solvent. If injection of a higher concentrationsurfactant is necessary at the particular site, one of ordinary skill inthe art could use membrane-based systems, such as Micellar EnhancedUltrafiltration (MEUF), to recover and reuse the surfactant. (Lipe etal., 1996; Sabatini et al., 1998b.)

Chemical Oxidation as a Polishing Step. In the presently claimed anddisclosed invention, surfactant flushing is followed by a polishingstage utilizing the introduction of a chemical oxidant to substantiallydegrade the contaminant left in the soil and groundwater subsequent tothe surfactant flushing step. Bench-scale experiments are conducted toevaluate the effectiveness of in-situ chemical oxidation in order toillustrate and evaluate the primary performance characteristics of thetechnology, including (1) oxidant-contaminant reaction kinetics, (2)matrix interactions and other secondary geochemical effects, (3)subsurface oxidant transport, (4) overall oxidant consumption, and (5)contaminants treated and overall reductions achieved.

Chemical Oxidant Selection and System Design. The first step in theprocess of chemical oxidant polishing is selecting the proper oxidantfor the site. The two most common oxidants used for process applicationsare hydrogen peroxide, or modified Fenton's Reagent (with a catalystadded under higher or neutral pH), which will be applied at the activepetroleum gas station and/or active chemical plants to minimize thecorrosion of the metal fittings and pipings, and potassium permanganate,however sodium permanganate, ozone, chlorine dioxide, dissolved oxygenor any other oxidant, in which a person having ordinary skill in the artmay be familiar, may be tested and be used in this system. To ensure asuccessful project, several design steps of a chemical oxidationpolishing system should be satisfied. An understanding of relativereaction rates and the life span of reactants are required to ensureadequate contact time for the desired reactions. The chemical demandassociated with pH adjustment is evaluated since many of the oxidationreactions are pH-dependant. In addition, geochemical characteristics ofthe site are identified to help predict how naturally occurring mineraland organic fractions within the soil and ground water will affect theprocess.

Before installing a field-scale chemical oxidation system, certain datais be collected to ensure proper chemical addition ratios and reactiontimes are achieved at the site. This information may include, but is notlimited to, data on the reaction kinetics, pH conditions, and naturallyoccurring interference within the subsurface for the specific site. Inaddition, mobility control and transport of the injected oxidant to thetarget areas is crucial, especially at a site with less of apermeability zone and having high organic and mineral interference.

Degradation Test. Similar to surfactant screening tests, bench-scaleoxidation degradation studies (i.e., batch tests and one-dimensionalcolumn studies) are performed in the laboratory to investigate thereaction rates and mechanisms for the previously discussed oxidantsusing soils, NAPL (if available), and contaminated groundwater collectedfrom the demonstration site. In the laboratory batch tests/kineticstudies, the samples are prepared in the reactor (e.g., 40 ml EPA vials)spiked with site contaminants (i.e., LNAPL and/or DNAPL) at thepre-determined concentrations (from high ug/L to low mg/L). These arethe typical pollutant levels observed at the dilute plume area and/orafter most NAPL mass has been removed from the contaminant source area.The Fenton's reagent and permanganate constituents, required to promotethe respective oxidation reactions, are added to the reactor (e.g., 40mL vials) at concentrations between 500 mg/L to ten percent. The samplesare equilibrated for various reaction periods (from hours to days) atthe demonstration site groundwater temperature. The final contaminant(s)and oxidant concentrations are measured. Changes of reaction parameters,such as pH and redox potential, Eh, are recorded. The reaction rateconstants are calculated to quantify the removal of contaminant(s).

In addition, the demand for pH adjustment during chemical oxidation isevaluated, since many of the reactions involved are pH dependent.Maintaining the proper pH conditions for Fenton's oxidation is crucialto the availability of the ferrous ion (Fe²⁺) catalyst. The buffercapacity of the soil determines whether pH adjustment for chemicaloxidation is effective and/or economical. To evaluate the effects of pH,testing is performed using potassium permanganate and Fenton's reagentunder acidic, neutral, and basic conditions. Similar batch/kinetic testsfor varying solution pH are conducted as previously described. Soil andgroundwater conditions can affect chemical oxidation performance throughdirect competition with contaminants for the oxidant and should,therefore, be taken into account.

The primary interference with Fenton's oxidation is carbonate andbicarbonate, which influence pH conditions and compete with contaminantsfor the hydroxyl radical. Elevated soil organic matters react withFenton's reagent and potassium permanganate. Oxidation of heavy metals,such as trivalent chromium (Cr(III)), remobilize the toxic form ofmetals like hexavalent chromium, Cr(VI), and therefore increase theunwanted risk at the site. If potential risk of remediation of Cr ispresent, additional tests are conducted to address these concernsdepending on the selected site conditions (e.g. Cr desorption test inthe soil peak columns). Typically, a phased approach is used tostreamline the tests and minimize the number of tests. This can beachieved by evaluating the degradation rates of the targeted pollutantusing the potential oxidants in a batch experiment. Only those oxidantswith favorable degradation rates will be further investigated on theirconsumption rate with the site-specific soil. The chemical oxidant withminimum mass losses to the soil is thereafter tested in aone-dimensional column or a two-dimensional sand tank in order tooptimize their conditions for complete degradation of pollutant infield. The optimal chemical oxidation system is thereafter able to beselected for the field application and is therefore site specific orsite optimized.

EXAMPLE 1

Sequent Surfactant Flushing and Chemical Oxidation for LNAPLRemediation—a Gasoline-Contaminated Underground Storage Tank (UST) Site.

A particular gasoline contaminated-site is located in the southeasternOklahoma town of Golden. The main contaminant is gasoline fuel as aresult of the leakage of USTs from two former corner gas stations. Depthto the contaminated zone was 5 to 25-feet. Most free phase LNAPLs weretrapped in the shallow zone (5 to 15 ft) containing sandy silt, siltyclay, and silt. The treated area covered approximately 25,000 ft². Theprimary goal of the project was to remove all free phase gasoline. Thesecondary goal was to demonstrate a significant decrease in soil andgroundwater concentrations (one to two orders of magnitude). Thetertiary goal was to see how low the final contaminant concentration ingroundwater could be achieved, to approach the Maximum Contaminant Level(MCL).

Before field implementation, Golden site LNAPL, and soil and groundwatersamples were obtained and used to screen for the optimal surfactantsystems. In the laboratory screening experiments, four anionicsurfactant/co-surfactant mixtures were investigated for their potentialuse in remediating Golden LNAPL (fuel gasoline) with the in situsurfactant flushing technology disclosed and claimed herein. Theselected surfactant/co-surfactant included mixtures of (1) sodiumdioctylsulfosuccinate (AOT:75% active. Aerosol OT 75% PG surfactant, byCytec Industries, Inc., West Paterson, N.J., USA) and sodiumdihexylsulfosuccinate (AMA), (2) AOT and polyoxyethylene sorbitanmonooleate (Tween 80), (3) AOT and linear alkyl diphenyloxidedisulfonate (Calfax 16 L-35% active, by Pilot Chemical Company, Santa FeSprings, Calif., USA), and (4) Alkylamine sodium sulfonate (LubrizolDP10052) and AMA. All surfactant solutions were prepared according totheir percent activity. For example, a 100 g 0.75% AOT solution isprepared by adding 1 g of AOT raw material (75% active) to 99 g of H₂O(water). The laboratory screening activities consisted of numerous testsincluding surfactant-NAPL phase behaviors, surfactant sorption andprecipitation, and contaminant extraction-column studies as describedpreviously in the experiment methodology section (also see Shiau et.al., 1994; Shiau et. al. 1995; Shiau, et. al. 2000). As shown in Table1, batch surfactant screening experiments indicate that all foursurfactant mixtures used can achieve Winsor Type III (middle-phase)microemulsion with Golden site NAPL, mostly at total surfactantconcentration less than 1 wt %. TABLE 1 Summary of Surfactant/NAPL PhaseBehaviors NAPL (TPH) solubility Equilibrated Surfactant at optimal Timeof Stable Concentration Appearance of Type III Type III Evaluated WinsorType III system Microemulsion¹ Surfactant System wt % Microemulsion mg/L(hr) AOT/AMA   1 to 2 transparent 440,000 1 to 2 AOT/Tween 80 0.2 to 1translucent 400,000  8 to 12 AOT/Calfax16L-35² 0.2 to 1 translucent450,000 1 to 2 Lubrizol DP/AMA³ 0.2 to 1 opaque 400,000  8 to 12¹NaCl (ranging from 0.1 to 3 wt %) was used to achieve the optimal TypeI system at various ratios of surfactant mixtures²Surfactant system used at Golden UST site³A small portion of the contaminated zone was treated with thissurfactant

Table IA illustrates the formulation of the preferred surfactant systemAOT/Calfax 16L-35 used at the Golden site for gasoline clean-up. Alsosurfactant formulations for other contaminants, such as diesel fuel andTCE, are also listed in Table IA. TABLE IA Surfactant Co-surfactantElectrolyte Type of Contaminants wt % wt % wt % Microemulsion GasolineDioctylsulfosuccinate sodium linear NaCl Winsor Type III (AOT) alkyldiphenyloxide disulfonate (Calfax 16L-35) 0.75 0.19 1.2 Diesel Fueldioctylsulfosuccinate sodium linear NaCl Winsor Type III (AOT) alkyldiphenyloxide disulfonate (Calfax 16L-35) 0.75 0.19 1.7 TCEDioctylsulfosuccinate sodium linear NaCl Winsor Type III (AOT) alkyldiphenyloxide disulfonate (Calfax 16L-35) 0.77 0.27  1.84

The screening tests were conducted at different surfactant/co-surfactantratios by adding various amounts of NaCl to promote the formation of amiddle-phase (or Winsor Type III) microemulsion. In these tests, a lowsurfactant concentration (<1 wt %) approach was found to significantlyimprove the cost effectiveness of the site clean-up effort. Based on thescreening tests, it was concluded that one surfactant system was thebest candidate for the site-specific conditions (i.e., able to produce atranslucent middle-phase microemulsion with ultra-low interfacialtension at value <0.005 dyne/cm and the highest NAPL solubility): acombination of anionic surfactant mixture, AOT/Calfax 16L-35 (totalconcentration=0.94 wt %) at AOT/Calfax weight ratio (wt %/wt %) of0.75/0.19 with 1.2 wt % NaCl added. The prepared formulation is shown inTable IA.

For the polishing step, abiotic chemical oxidation was used to treat theresidual oil and dilute plume at the shallow zone of this site theGolden site. Both Fenton's Reagent and potassium permanganate wereevaluated. As shown in Table 2, at a low concentration of chemicaloxidant, Fenton's Reagent appeared to be more favorable in treating theBTEX compounds found at the site. TABLE 2 Representative Results of BTEXDegradation with Fenton's Reagent m, p- Fenton's Benzene¹ % Toluene %Ethylbenzene % Xylene % o-Xylene % Reagent Used reduction reductionreduction reduction reduction H₂O₂ = 2,000 mg/L 92 44 59 47 44 Fe⁺² = 90mg/L pH = 2 to 3 adjusted by 50% H₂SO₄ H₂O₂ = 2,000 mg/L 93 NA² NA NA NAFe⁺² = 90 mg/L pH = 2 to 3 adjusted by 50% H₂SO₄ ² KMnO₄ = 5,000 mg/L³ 8NA NA NA NA¹Initial BTEX mixtures containing 1,000 ug/L of individual compound;reaction time = 12 hr²Initial benzene-only concentration = 4,000 ug/L; NA = not available³Initial benzene-only concentration = 1,000 ug/L

For example, 93% of the initial 4,000 μg/L benzene was degraded using aFenton's Reagent, containing H₂O₂, 2,000 mg/L, Fe⁺², 90 mg/L, pH value @2 to 3. Benzene degradation was only 8% of the initial 1,000 μg/Lbenzene after a 5,000 mg/L KMnO₄ solution was added.

As shown in Table 3, one-dimensional column tests were conducted toassess the contaminant removal under hydrodynamic condition. Injectionof a one pore volume of AOT/Calfax (0.94%) mixture was able tomobilize >90% of the trapped LNAPL from the 1-D column. TABLE 3 Summaryof 1-D Column Study Results Post-surfactant Post-surfactant + (Step 1)chemoxid (Step 2) Total % contaminant % contaminant contaminant ProcessUsed removed removed removal % Step 1: 91¹ 8.6² 99.6² Surfactant:AOT/Calfax (0.94 wt %) + NaCl 1.2 wt % (1PV) Step 2: Fenton's Reagent:H₂O₂ (0.4 wt %) Fe⁺² (90 mg/L) pH = 2.6¹Estimated based on the mobilized NAPL volume and dissolved NAPL data;initial column oil saturation = 2%²Based on final soil extraction measurement

Fenton's Reagent was selected to polish the residual NAPL after thesurfactant flood. Representative column results are shown in FIG. 2 andTable 3. In the soil column, the total NAPL removed (measured by totalpetroleum hydrocarbon, TPH, or gasoline range organics, GRO) was 99.6%.Without the polishing step (chemical oxidation), the surfactant flushingalone could not achieve remediation to an extremely low contaminantlevel in the soil. Direct injection of a high concentration Fenton'sReagent (H₂O₂ level at 10 wt %) would have required multiple porevolumes (>5 PV) to achieve 80% to 90% contaminant removal (data notshown). Therefore, laboratory experiments indicated that integratedsurfactant flushing followed by chemical oxidation would be able totreat the Golden site NAPL to extreme low level concentrations (low ppbrange).

In situ surfactant flushing was used to recover free phase LNAPL(gasoline) using the low concentration surfactant (<1 wt %) andpolishing oxidant methodology of the presently disclosed and claimedinvention. One pore volume of 0.94 wt % AOT-Galfax16L-35 (Table IA)surfactant (190,000 gallons) was injected into the contaminated shallowzone (source area, mostly silty material) over a two month period tomobilize the trapped NAPL. Initial free phase gasoline thickness on thewater table ranged between 2.7 feet to 3.3 feet. Representative resultsfrom the field remediation effort at the Golden UST site are shown inFIGS. 3 and 4 and in Tables 4 and 5. TABLE 4 Representative ContaminantConcentration in Golden Soil before and after the Sequent SurfactantFlushing and Chemical Oxidation Soil Sample Comparison Data Pre-Flushvs. Post Flush Calfax/AOT Flush TPH- Percent Percent Sample DepthBenzene Toluene Ethylbenzene Xylenes Gro Reduction Reduction Number ft.bgl. ug/kg ug/kg ug/kg Ug/kg mg/kg Benzene TPH-Gro MLS-1A 12.5 13400.058100.0 18800.0 92700.0 809.0 PTGP-2A 12.5 511.0 9970.0 3520.0 20600.0164.0 96.2 79.7 MLS-1B 14.0 16000.0 185000.0 85300.0 454000.0 3630.0PTGP-2B 14.0 2350.0 37300.0 14600.0 78600.0 548.0 85.3 84.9 MLS-2A 12.531800.0 438000.0 114000.0 595000.0 5080.0 GP-7A 12.5 2400.0 41800.017100.0 95700.0 691.0 PTGP-9A 12.5 225.0 476.0 ND ND 56.0 99.3 98.9MLS-2B 14.0 4980.0 26700.0 6640.0 38100.0 345.0 PTGP-9B 14.0 284.0 ND527.0 3790.0 59.0 94.3 82.9 DW-1A 11.0 1900.0 14900.0 8750.0 48400.0355.0 PTGP-1A 11.0 ND ND ND ND 4.2 >99 98.8 DW-1B 14.0 11200.0 99800.044900.0 250000.0 2190.0 PTGP-1B 14.0 2670.0 4920.0 7580.0 28400.0 137.076.2 93.7 DW-5A¹ 14.0 20800.0 148000.0 58800.0 326000.0 2780.0 GP-6B14.0 1210.0 12720.0 5820.0 31900.0 325.0 94.2 88.3 DW-8A 14.0 41100.0182000.0 54600.0 277000.0 2560.0 PTGP-10A 14.0 1060.0 42700.0 19700.0104000.0 890.0 97.4 65.2 DW-16A¹ 11.0 9720.0 277000.0 129000.0 707000.05740.0 PTGP-12A 11.0 ND 118.0 ND ND 19.0 >99 99.7Notes:BackgroundConcentration¹The 14 foot sample for DW-5A and DW-16A denotes the 14 foot depth,unlike DW-1A.

TABLE 5 Oklahoma Corporation Commission (OCC)/U.S. EnvironmentalProtection Agency (U.S. EPA) Post Test Soil Sample Results Sample DepthConcentration, mg/kg I.D. Ft. bgl. benzene Toluene ethylbenzene xylenesTPH-Gro PB-1 15.8 0.425 1.93 1.12 4.29 88.3 PB-2 16.7 0.103 0.170 0.0350.190 1.83 PB-2 18.5 2.27 8.07 2.390 13.4 111.0 PB-3 17.7 0.295 3.021.20 6.87 54.5 PB-3 18.5 0.165 0.374 0.054 0.299 2.40 PB-4 17.0 4.2416.7 4.14 21.6 155 PB-5 10.2 0.072 0.675 0.28 1.86 18.8 PB-5 17.3 0.7276.31 2.18 13.1 160.0

No visible or instrumental evidence of free phase gasoline was detectedin 25 recovery and monitoring wells (three out of 28 wells had minimalthicknesses) during the post surfactant sampling event (FIG. 3). Theobserved benzene concentration indicated that 75%-99% reduction in soilconcentrations were achieved during the surfactant flush (FIG. 4 andTable 4). Similarly, a reduction of TPH (GRO) concentrations in thesoils was between 65%-99%. After surfactant flushing, the remainingtrace residual and dissolved NAPL were treated by the final polishingsteps using chemical oxidation in the shallow zone, where most NAPL waspresent before the surfactant flushing. Representative soilconcentrations after the post-oxidation phase are summarized in Table 5.As shown in Tables 4 and 5, further contaminant reduction/degradation(OCC/EPA soil sampling event held in June, 2002) was observed after thepost-polishing step was completed. These results indicate that theintegrated surfactant flushing and chemical oxidation methodology of thepresently disclosed and claimed invention is capable of remediatingcontaminants to substantially non-detected or extremely low level, ifnot completely removed, in a “real world” field-scale test.

EXAMPLE 2

Sequent Surfactant Flushing and Chemical Oxidation Polishing for DNAPL—aTCE-Contaminated Site.

The targeted site was contaminated by TCE, a DNAPL and common degreaser.The main focus of this experiment was to treat the dilute TCE plume withan in-situ chemical oxidation process. This approach was selected ratherthan treating the source zone NAPL because the DNAPL source zones couldnot be identified. Most laboratory efforts were focused on evaluatingthe effectiveness of two selected oxidants, potassium permanganate(KmnO₄) and Fenton's reagent, for TCE and cis-DCE degradation. A limitedeffort was given to evaluate the effectiveness of sequent surfactantflushing and chemical oxidation to treat the TCE-contaminated source (orhot) zone.

Use of Potassium Permanganate for TCE/DCE Degradation

Batch experiments were conducted to evaluate the degradation rates ofTCE, cis-DCE, or their mixture by KMnO₄. These experiments were carriedout in TCE/DCE dissolved solutions in the absence (Table 6) or presence(Table 7) of site-specific soil. As shown in Table 6, 250 mg/L KMnO₄ candegrade TCE or DCE completely at low contaminant levels. Initialcontaminant concentrations ranged from several hundred of ug/L to morethan 100 mg/L. As shown in Table 7, KMnO₄ concentrations ranging from 10mg/L up to 10,000 mg/L (1%) solution were tested. Results indicated thatmost reactions between KMnO₄ and TCE, DCE, and TCE/DCE mixtures (betweenfew hundreds ppb to 5 ppm) were complete after a 24-hr reaction period.TABLE 6 Degradation Reaction of KMnO₄ and low level of TCE, DCE andtheir mixtures without soil KMnO4 TCE, DCE Final TCE Final DCE added, %% SAMPLE ID ug/L ug/L mg/L degraded degraded DCE-C-8 8 4820 0 NA 0(control) DCE-100-8 3 691 100 NA 85.7 DCE-250-8 0 22 250 NA 99.5 TCE-C-8283 0 0  0 NA (control) TCE-100-8 0 1 100 100 NA TCE-250-8 0 1 250 100NA D&T-C-8 70 1407 0  0 0 (control) D&T-100-8 0 14 100 100 99.0D&T-250-8 0 11 250 100 99.2Note:-8 samples were analyzed after 29 hrs of sample preparation.

TABLE 7 Degradation Reaction of KMnO₄ and TCE, DCE and their mixtureswith two types of soil (Soil 1-26′-27′; Soil 2-18′-20′, in 40 mLsolution) Final KMnO₄ TCE Final DCE added TCE % DCE Sample ug/L ug/Lmg/L degraded % degraded SDCE-C 18 5486 0 NA 0 SDCE-100 0 17 100 NA 99.7SDCE-250 0 16 250 NA 99.7 STCE-C 237 0 0  0 NA STCE-100 0 0 100 100 NASTCE-250 0 0 250 100 NA ST&D-C 117 2432 0  0 0 ST&D-100 0 13 100 10099.5 ST&D-250 0 12 250 100 99.5

Most reactions between KMnO₄ and TCE/DCE are completed in less than onehour under room temperature (20° C.). As shown in Table 8, experimentsconducted with soil added indicate that complete degradation of TCE andDCE was observed under similar conditions. TABLE 8 Degradation Reactionof KMnO₄ and high level of TCE without soil Initial KMnO₄ Final TCEadded TCE Sample ID mg/L mg/L % degraded Control 343 0.0 0 T10000 0.010,000 100 T5000 0.0 5,000 100 T1000 0.0 1,000 100 T500 111 500 67.7

The loss of KMnO₄ in two soil samples collected from the site weredetermined to be negligible during 4-, 7-, and 14-days of reactionperiod (data not shown). Low sorption loss of KMnO₄ reduced the amountof KMnO₄ required and the total cost of remediation project.

Under higher initial TCE levels (>300 mg/L), results indicate thatadding 1,000 mg/L or more KMnO₄ completely degraded the added TCE. A67.7% reduction of TCE was observed with 500 mg/L of KMnO₄ solution.

Batch study indicated that addition of potassium permanganate degradeddissolved TCE and DCE in the dilute plume near the vicinity of the soilsampling locations. In addition, other loss mechanisms for permanganateincluding sorption and fortuitous reactions with other reduced compoundswere minimal in the tested samples.

Use of Fenton's Reagent for TCE/DCE Degradation.

Fenton's reagent is the second oxidant tested. Fenton's reagent wasprepared by dissolving H₂O₂ and catalysis Fe(II) (FeCl₂ or FeSO₄) inacidic solution (HCl or H₂SO₄).

Batch results indicated that Fenton's reagent degrades both TCE and DCE,but appears less efficient compared to KMnO₄ on a weight basis. Forexample, 283 ug/L TCE can be completely degraded by 100 mg/L KMnO₄solution, yet 100 mg/L H₂O₂/FeCl₂ solution only oxidize 51.7% of TCE.For similar contaminant concentrations, DCE degradation required moreFenton's reagent than TCE. Note that some pollutants, such astrichloroethane (TCA) or BTEX, could not be completely degraded byKMnO4, but will be degraded effectively by Fenton's reagent.

The batch studies clearly indicate that both KMnO₄ and Fenton's reagentwere candidates for degrading the target contaminant, TCE, and thecommon intermediate, DCE, at the selected sampling locations at theDNAPL-impacted site.

1-D Column Study with KMnO₄-only for TCE Removal.

Several column tests were conducted by injecting KMnO₄ at differentconcentrations (100, 500, 5000, 20000 mg/L) under various TCE residualsaturation in the soil packed column. In the column study, fifteen totwenty five pore volumes of KMnO₄ were injected to evaluate the removalof TCE under the hydrodynamic conditions.

At a 1% initial TCE residual saturation, significant gas bubbles (mainlyCO₂ gas) were observed in the effluent after a 5,000-mg/L KMnO₄ solutionwas injected, while TCE concentration also began to drop significantly(to less than 10 mg/L level). In another column test, a 10% TCE residualsaturation was used with various KMnO₄ levels being injected (100, 500,5,000, 20,000 mg/L). Similarly, numerous gas bubbles were created whenhigher KMnO₄ concentrations were injected (5,000 mg/L and above) (datanot shown). In addition, dark brown MnO₂ precipitates were accumulatedat various locations in the column.

After the KMnO₄ flushing, the treated column was dismantled and the soilwas extracted with methanol to determine the final TCE concentration.The final TCE concentrations in the column ranged from 8 mg/Kg to 47mg/Kg in different columns (both low and high initial TCE levels). Asignificant amount of TCE was degraded with KMnO₄ flushing. However, asignificant release of CO₂ near the NAPL source area could potentiallychange the hydraulic permeability of the aquifer and lead to by-passaround the TCE ganglia preventing further removal, as other researchershave suggested. In addition, significant accumulation of MnO₂precipitates at the interface of NAPL and water also reduce the masstransfer of KMnO₄ to TCE and decrease the TCE degradation rate. Thisproblem has been observed in field trials with KMnO₄ and is a limitationof the technology for remediation of a contaminated hot zone. Resultsfrom these column tests indicate that injection of KMnO₄ alone couldeffectively degrade TCE under proper conditions, such as for aTCE-impacted dissolved plume but not in areas with free phase DNAPL orhigh level of TCE residual saturation. Chemical oxidation is veryeffective for degrading a TCE dilute plume or as a polishing-step forsource zone remediation after the majority of the TCE is removed by thesurfactant flooding. The relatively low quantity of remaining TCE wouldbe less likely to cause manganese precipitation and hydraulic bypassingupon reaction with KMnO₄.

1-D Column Study with Sequent Surfactant Flushing and Chemical Oxidation(KMnO₄) Flushing for TCE Removal.

Additional column tests were conducted using surfactant flushing tofirst remove significant TCE NAPL mass, followed by KMnO₄ flushing todegrade the TCE left in the column. Examples of the column study resultsare shown in FIG. 5. Initial TCE residual saturation was 2%. At 4 PV, asurfactant solution, containing 2.5% dihexyl sulfosuccinate (AMA), 5%diphenyl oxide disulfonate (Calfax), 3% NaCl, and 1% CaCl₂, was injectedinto the column. The selection of this surfactant system was based on aprevious field test done for a mixed DNAPL contaminated site, containingtricholorethane (TCA), TCE, DCA, and DEC. The enhancement of TCAsolubility with the selected surfactant system (Calfax/AMA/CaCl₂/NaCl)is listed in Table 9. TABLE 9 Comparison of Trichloroethane (TCA)Solubilization in Batch and Column Studies Maximum TCA TCA Solubilizedin Solubilized in column Surfactant System Batch test (mg/L)¹ test(mg/L) Dowfax/AMA/NaCl/CaCl₂ 99,259 168,996 Lubrizol71/IPA/NaCl/ 259,355NA³ CaCl₂¹Volume determined by volumetric addition of TCA during the phasebehavior study²Surfactant used in the sequent surfactant flushing/chemical oxidationtest³NA = not available

A surfactant system used for TCA could be used for TCE (with similarhydrophobicity property) to produce a middle-phase microemulsion.Therefore, a mixture of Calfax/AMA surfactant was used to conduct this1-D column test. Significant TCE mass (concentration reached 100,000mg/L) was removed from the column after surfactant breakthrough. After 5PV of surfactant flushing, a 2,000 mg/L KMnO₄ solution was injected tofurther degrade the TCE in the column. A total of 4 PV of KMnO₄ solutionwas injected in the column before post-water flushing began at 12 PVinjection time.

Significant TCE mass was removed during the surfactant flushing period.A decrease of the TCE concentration, eventually below the quantificationlimit, after the KMnO₄ breakthrough, is also clearly demonstrated. Postcolumn extraction indicated that 99.94% of the initial TCE was removedfrom the column. Note that the surfactant concentration used in thiscolumn test was 7.5 wt %. As shown in Table 10, a recent batch studyconducted by Applicant indicates that a low surfactant concentration (<1wt %) could achieve similar solubility enhancement for TCE. TABLE 10Solubilization of DNAPL (TCE) Using Low Surfactant Concentration (1 wt%) TCE Solubilized in Sample bacth test Note Name Phase mg/L 1 wt %surfactant fb-015s middle 177104 Calfax/AOT fb-015s aqueous 99577Calfax/AOT fb-014s middle 383813 Calfax/AOT fb-014s aqueous 66677Calfax/AOT fb-008 aqueous 152882 Lubrizol System

Therefore, a surfactant flushing with a low surfactant concentrationsystem (e.g., Calfax/AOT—see Table IA for TCE) followed by a chemicaloxidation step significantly improves the state of the art and makes ittechnologically and economically viable to completely remediatecontaminated sites.

Complex Viscous Non-aqueous Phase Liquids.

An additional embodiment of the currently disclosed and claimedinvention pertains to a surfactant flushing system that is capable ofremediating soil and groundwater that has been contaminated by orimpacted by complex viscous NAPLs. Injection of a selected biodegradableco-solvents at predetermined volumes prior to injecting a pre-selectedsurfactant (as described hereinabove) significantly enhances theperformance of such a surfactant flushing step for recovering highlyviscous oils or NAPLs. Suitable biodegradable co-solvents for use in thepresently disclosed and claimed invention include, without limitation,the oil derivatives from natural/engineered agriculture edible fats andoily products, such as soybean oil, canola oil, citrus, grape oil,vegetable oils as well as combinations or derivations thereof.

Examples of suitable biodegradable co-solvents include methyl and ethylesters of fatty acids. Two particular examples are SoyGold® 2000 (CASNo. 67784-80-9, AG. Environmental Products, Lenexa, Kans., U.S.A) andSoyGold® 1000 (CAS No. 67784-80-9) (similar to SoyGold® 2000 but with nosurfactant added). The SoyGold® 2000 co-solvent is a fatty acid methylesters, with alkyl chain C16-C18, or methyl esters of soybean oil. Anamount of the biodegradable co-solvent may also include trace amounts ofone or more surfactants in order to increase the biodegradableco-solvent's dispersivity in the water. For viscous fluids (i.e. thosefluids having a viscosity between 50 cp to 1500 cp or higher), in oneembodiment the alkyl chain is a C12-C24 chain having a viscosity rangeof between 1 to 20 cp for easy delivery and enhanced injectivity in thesubsurface.

One of the considerations for successful delivery of the biodegradableco-solvent in the subsurface is that any such biodegradable co-solventshould be miscible in water. Therefore, in addition to the goodbiodegradability, the dispersivity of these co-solvents in water shouldbe carefully evaluated before field implementation. Without gooddispersivity in water, the injected co-solvent might separate intodifferent phases in the soil and dramatically reduce their effectivenesson oil recovery. Another example of the biodegradable co-solvent for thepresently claimed and disclosed invention is d'Limonene (CAS No.5989-27-5, Florida Chemical Company, Inc., Winter Haven, Fla.). Thed-Limonene is the major component of the oil extracted from citrus rind.Additional co-solvents may be considered for the environmental clean-upapplication but less environmentally desirable may include naphtha,mineral spirit, mid to long chain alcohols (>C5) and otherpetroleum-based solvents.

For remediation of complex viscous oils impacted soil and groundwater,pre-injection of 0.02 to 0.5 pore volume (PV) of the selectedbiodegradable co-solvent, documented in the presently claimed anddisclosed invention enhances the effectiveness of the surfactant systemfor mobilization of the trapped oil as described previously in U.S. Pat.No. 6,913,419 and U.S. Pat. No. 7,021,863, entitled “In situ surfactantand chemical oxidant flushing for complete remediation of contaminantsand methods of using the same”, the specification which is herebyexpressly incorporated in its entirety herein by reference. Addition ofbiodegradable co-solvent before surfactant injection may have multiplepurposes, including decreasing the viscosity of the target contaminants,promoting the desorption of the trapped oils from the soil, and likelyimproving sweep efficiency in conjunction with the surfactant (and thepolymer) flushing.

The ideal surfactant system may be selected based on their capability toform the middle phase microemulsions (or achieving ultra-low interfacialtention) between the target contaminant and the surfactant as describedin detail previously in U.S. Pat. No. 6,913,419 and U.S. Pat. No.7,021,863, entitled “In situ surfactant and chemical oxidant flushingfor complete remediation of contaminants and methods of using the same”,the specification which is hereby expressly incorporated in its entiretyherein by reference. One example is a mixture of doctylsulfosuccinate(AOT) and sodium linear alkyl diphenyloxide disulfonate (Calfax 16L-35)with surfactant concentration, listed previously in U.S. Pat. No.6,913,419 and U.S. Pat. No. 7,021,863, entitled “In situ surfactant andchemical oxidant flushing for complete remediation of contaminants andmethods of using the same”, the specification which is hereby expresslyincorporated in its entirety herein by reference, would produce themiddle phase microemulsions for a variety of complex viscous oils,including coal tars, heating oils, creosote and others as describedpreviously in U.S. Pat. No. 6,913,419 and U.S. Pat. No. 7,021,863,entitled “In situ surfactant and chemical oxidant flushing for completeremediation of contaminants and methods of using the same”, thespecification which is hereby expressly incorporated in its entiretyherein by reference. The target pore volume (PV) for the surfactantflushing (or surfactant injection) which followed the co-solventinjection may be between 1 to 5 PV. In general, a combination ofsurfactant solution and a selected polymer solution may be injectedsimultaneously to improve the sweep of the flushing on NAPL removed.After the surfactant flushing, a freshwater, or recycled treated waterfrom the recovered fluid may be used to further mobilize the releasedcomplex viscous NAPL until most NAPL have been captured and recovered.This post-surfactant water flushing may last one to three pore volumes.Thus, by combining the co-solvent pre-injection and surfactant with apolymer drive and post-water flushing as described in this invention,significant amounts of complex viscous oil (likely greater than 90% ofinitial trapped oil) could be removed from the subject site. Aftermajority of the NAPL been removed, one can then use chemical oxidantinjection as described in prior invention to further treat the diluteplume to achieve the clean-up levels and close the site.

One advantage of this invention is that no (or minimum) addition of heator thermal energy is required to achieve the goal of removing thecomplex viscous oils. This is a significant improvement on the projectcost and design of the equipment for the above-ground water treatmentsystem. Another benefit of this invention is that the biodegradableco-solvent left in the soil and groundwater after completion of theproject may be easily degraded by the native microorganisms under thesite-specific conditions. In addition, these viscous oils may be trappedunder the existing building or in a deeper subsurface zone (>30 ft depthbelow ground surface, bgs), in situ surfactant flushing with help frompre-injection of biodegradable co-solvents may be one of the very fewtechnologies which can access the contaminants without digging asignificant amount of site soil before removing the contaminants.

EXAMPLE 3

A viscous coal tar sample (a dense non-aqueous phase liquid DNAPL) wasretrieved from a contaminated site located in northeast part of U.S.A.The site-specific coal tar DNAPL viscosity is close to 40 cp at 20° C.(63 cp at 15° C.) measured in this study. The site-specific DNAPL, soil,and groundwater samples were obtained and used to screen for the optimalsurfactant system(s). In the laboratory screening experiments, a mixtureof anionic sulfosuccinate (AOT or so called DOSS-70)/dialkyldisulfonated diphenyl oxide (Calfax-16L)/NaCl surfactants wereinvestigated for their potential use in remediation of the DNAPL withthe in situ surfactant flushing technology. The phase behavior studyindicated a mixture of 0.75 wt % AOT, 0.19 wt % dialkyl disulfonateddiphenyl oxides surfactant and 1.7 wt % NaCl solution (previous patentedsurfactant formulation) may achieve the optimal middle phasemicroemulsion for this DNAPL. Therefore, this surfactant system wasselected for further one-dimensional (1-D) column study to evaluate thecoal tar oil removal efficacy in the sand-packed columns (see Table 1).As common practice, a polymer solution was used to enhance the mobilitycontrol of the mobilized viscous oil. In addition to surfactantflushing-alone, a combination of pre-flushing biodegradable co-solvent(0.25 PV) and injection of the selected surfactant system was assessedto evaluate the enhancement of biodegradable co-solvent on theperformance of oil removal in the soil. TABLE 11 Summary of SelectedColumn Test Results Parameter Column #2 Column #4 Column #6 Surfactantused 1.25 PV, 0.75 wt % 2 PV, 0.75% AOT 2 PV, 0.75% AOT (or AOT (orDOSS)/ (or DOSS)/0.19 wt % DOSS)/0.19 wt % 0.19% Calfax/1.7 wt %Calfax/1.7 wt % Calfax/1.7 wt % NaCl NaCl NaCl with (Pre-flushed with pHadjusted by 0.25 PV co-solvent NaOH (˜40 mg/L) SoyGold ® 2000 - to 1197% active) Polymer drive 1.25PV, 1200 mg/L 2 PV, 1500 mg/L 2 PV, 1500mg/L AP-1120 (dissolved FLOPAAM 3630 FLOPAAM 3630 (co- and co-injected(co-injected w/ injected w/ with surfactant) surfactant) surfactant)Post flush 1 PV tap water 3 PV tap water 3 PV tap water free product 6.2ml (initial 6.2 ml (initial 6.2 ml (initial added added added in tocolumn added in) - 20% in) - 20% initial free product final packed withNorth initial residual residual saturation Shore site clean saturation0.1 ml left (5.3 ml soil)-20% initial 0.9 ml left (5.3 ml collected)NAPL residual collected) saturation* 1.2 ml left (4 ml collected) TotalNAPL 64.5% 85%* 98.5%* removed (%)*Site contaminated soil contained 8,600 mg/kg diesel range organicsmeasured by GC/FID (less than the 20% residual saturation used in the1-D column study)**Soil used in Column 2, 4 & 6: combined soil samples with hot airdried, passed through No. 12 sieve (=1.68 mm)

As determined from these laboratory results, significant free productNAPL (>95%) can be effectively removed (via mobilization) in a 1-Dcolumn packed with sieved fine sand material retrieved from the subjectsite using the developed pre-co-solvent and low surfactant and polymerflushing without adding the heat. The optimal surfactant system was ableto remove 64.5-85% of NAPL from the sand-packed column. Addition ofbio-degradable co-solvent with the surfactant flushing would furtherimprove the recovery of these complex viscous fluids. Therefore, theinvention of this process could save the remediation project cost andthe actual time frame for remediating the complex viscous fluids.

EXAMPLE 4

The second NAPL was a weathered No. 6 heating oil retrieved from a sitelocated in northeastern state of U.S. The heating oil was trapped underthe current building and required the remedial approach to remove thefree phase NAPL without impacting the routine activity of the building.A series of surfactant screening tests were conducted to select theoptimal surfactant system to mobilize the viscous oil. The site NAPLviscosity was more than 1,000 cp at 20° C. measured in this study. Theresulting surfactant-NAPL phase behavior studies are summarized in Table2. This table shows that the low interfacial tension of these systemsindicate the applicability of the selected surfactant system formobilization of this viscous heating oil. The observed middle phase (orWinsor Type III) microemulsion volume was negligible likely due to highviscosity of this NAPL (data not shown). The IFT measurement of NAPL andsurfactant solution indicated the optimal surfactant system occurs with2.1% NaCl added. Therefore, this dual surfactant system (0.75 wt % AOT(or DOSS)/0.19 wt % Calfax/2.1 wt % NaCl) was selected for furtherinvestigation in a one-dimensional column test. Removal of LNAPL will bemainly controlled by mobilization mechanism with this surfactant system.TABLE 12 Composition of surfactants and interfacial tension measurementsof the equilibrated phase Interfacial Surfactant Tension, IFT* Sample #Salinity (% NaCl) Dyne/cm A1 1.0 0.017 B1 1.3 0.034 C1 1.5 0.032 D1 1.90.021 E1 2.1 0.0073 F1 2.3 0.0077

*The formulations (0.75 wt % AOT/0.19 wt % Calfax in Sample# A1-F1 asdescribed previously in U.S. Pat. No. 6,913,41, entitled “In situsurfactant and chemical oxidant flushing for complete remediation ofcontaminants and methods of using the same”, the specification which ishereby expressly incorporated in its entirety herein by reference) formnegligible middle phases microemulsion (phase transition from WinsorType I to Type II directly). The optimal surfactant system contains 2.1%NaCl determined by the IFT measurement.

Typically, recovery of viscous free product NAPL may require addition ofa polymer (preferably non-toxic or low toxic compounds) dissolved in thesurfactant solution to increase the sweep efficiency of the mobilizedoil during the chemical flood. Under most conditions, addition of theselected polymer at low concentration levels of 500 mg/L to 2000 mg/L toenhance the performance of oil recovery may not pose any negative impacton the NAPL/surfactant microemulsion behavior. In addition, the materialsafety data sheets of the selected surfactants and polymers (allnon-toxic) and the bio-degradable co-solvents used in the site-specificlaboratory treatability studies should be provided to the Federal and/orState regulatory agencies before proceeding with the fieldimplementation tasks.

The optimal AOT/Calfax/NaCl surfactant system was investigated in theone-dimensional column study. Two non-toxic polymer systems, AP-1120 andFLOPAAM 3630, were selected for increasing the viscosity of thesurfactant solution. These polymers are anionic water-soluble polymersused as flocculant in water treatment plant (AP-1120) and/or forenhanced oil recovery (FLOPAAM 3630). The material safety data sheetsfor these surfactants and polymers are readily available for furtherconsideration of their applicability and injection into the subsurface.Initial column tests indicated that several challenges were met formobilization of this viscous NAPL. The selected liquid chromatographpump could not pump the site NAPL easily. Therefore, the subject sitesoil was pre-treated with site LNAPL to achieve 20% residualsaturation-impacted soil before packing into 1-D column. Use ofsurfactant/polymer flushing produced negligible NAPL removal (<10%)after 3 PV surfactant injection (data not shown in the Table 3).Additional column tests were conducted to evaluate enhanced NAPLrecovery by adding short chain alcohol (pentanol) or increase oftemperature (50° C.), yet no significant improvement was observed inthese efforts (data not shown in the table).

Further column tests indicated that injection of the biodegradableco-solvent SoyGold 2000® (between 0.25 PV to 2 PV were injected) topre-flush the site NAPL (viscosity>1000 cp @ 20° C.) in the sand-packedcolumn could dramatically increase the NAPL removal with the selectedsurfactant/polymer flush (greater than 90% NAPL removal). The selectedSoyGold 2000® for this study is nontoxic and easily biodegraded in thesoil based on the product information. Representative results of ColumnsNo. 6 & 7 are summarized in Table 3. Results show that the recovery ofNo. 6 heating oil NAPL using an integrated co-solvent pre-flush (0.25PV) and the surfactant/polymer flush was greater than 95%, as comparedto less than 10% NAPL removal with the surfactant/polymer-only flush.Therefore, pre-flushing the selected biodegradable co-solvent, such asmethyl esters of soybean oil along with the patented low surfactantsystem (AOT/Calfax) and polymer flush may provide significant advantagesfor site remediation of highly viscous oil, such as the weathered No. 6heating oil found at this contaminated site. It should be noted that atrace amount of SoyGold 2000® (close to 750 mg/Kg soil based on the DROsanalysis and the resulted chromatogram) was detected in the treated soilafter the pre-co-solvent and the surfactant/polymer flush. It isbelieved that this residual co-solvent will be easily biodegraded in thesoil in reasonable time frame or can be degraded by injection of lowchemical oxidant as a post-flushing polishing step (such as Fenton'sReagent) to reach non-detected level, if necessary. After a few weeks,the co-solvent left in the columns #6 and #7 was below thenon-detectable level, likely due to the biodegradation of oil underaerobic conditions. Typically, the oil degradation under anaerobiccondition would take a longer time frame to achieve a similar oildegradation. Based on the results of this study, one could anticipatethe residual co-solvent in the soil, after the flushing, to be degradedin one to a few months under anaerobic conditions.

Another advantage of injection bio-degradable co-solvent as listed inthis finding is the amount of co-solvent injected. We find only 0.02 to0.5 PV of bio-degradable co-solvent may be required to achievesignificant oil removal. Use of the common co-solvents, such as shortchain alcohol (butanol, iso-butanol, and pentanol) may require at leastone to several pore volumes (PV) injection before seeing significantimprovement of surfactant flushing and/or co-solvent-alone flushing.Minimizing the dosage of bio-degradable co-solvent may dramaticallyreduce the costs of above-ground treatment (and chemical use) toseparate the recovered NAPL and the co-solvent before recycling/reusethe recovered fluid and the final disposal of the recovered waste fluidand the contaminants. TABLE 13 Summary of Selected Column Test ResultsParameter Column #6 Column #7 Co-solvent pre-flush 1 PV, 97% SoyGold ®0.25 PV, 97% SoyGold ® 2000 2000 Surfactant used 3 PV, 0.75 wt % 3 PV,0.75 wt % AOT/ AOT/0.19 wt % Calfax/ 0.19 wt % Calfax/2.1 wt % 2.1 wt %NaCl NaCl Polymer drive 3 PV, 1500 mg/L 3 PV, 1500 mg/L FLOPAAM FLOPAAM3630 (co- 3630 (co-injected w/ surfactant) injected w/ surfactant) Postflush 3 PV tap water 3 PV tap water Initial NAPL concentration 31,235mg/Kg TPH* 14,484 mg/Kg TPH Final NAPL concentration 1,161 mg/Kg TPH 709mg/Kg TPH Total NAPL removed (%) 96.3%* 95.1%**TPH (diesel range organics) were measured by GC/FID with methylenechloride extraction.**Soil used in Columns #6 & #7: site soil sample was pre-washed withacetone, and hot air dried @ 200° C., and then was passed through No. 12sieve (=1.68 mm) before use; column tests were conducted @ 20° C.

It is anticipated that a polymer drive (using the selected polymers,either AP-1120 or FLOPAAM 3630) is required to have better sweepefficiency, as described herein. The added polymer (at concentrationbetween 500 mg/L to 2000 mg/L) was dissolved in the surfactant solutionand co-injected with the selected surfactant. In a separate study, morethan 90% of viscous No. 2 heating oil was removed by adding the polymerin surfactant solution compared to 10 to 20% NAPL removal withsurfactant-only system under similar conditions. Without better mobilitycontrol, the surfactant injected may generate a so-called “fingering”phenomenon that results in physical bypassing of the trapped NAPL phase.Polymer addition, for better mobility control, was commonly used in theenhanced-oil recovery. Therefore, an integrated pre-co-solvent andsurfactant/polymer flush is suitable for removal of the complex viscousoils found at various contaminated sites based on the results of thesestudies.

Although the present invention has been described in considerable detailwith reference to certain preferred versions thereof, other versions arepossible. For example, single surfactant systems such as anionic/anionicand nonionic/nonionic mixtures; surfactant systems such asanionic/cationic and anionic/nonionic mixtures; and contaminants such aspolyaromatic hydrocarbons (PAH), coal tars, creosote, crude oil,pesticides, polychorinated biphenyls (PCBs) and ketones can be utilizedwith this integrated approach. Therefore, the spirit and scope of theappended claims should not be limited to the description of thepreferred versions contained herein. In addition, further cost savingsand process improvements can be realized by recycling the recoveredbio-degradable co-solvent. In this group, ongoing research anddevelopment are focusing on optimizing the recycling/reuse processes totreat the recovered fluids, including mixtures of bio-degradableco-solvent and the recovered viscous NAPLS. After treatment, therecycled/reused bio-degradable co-solvent can be re-injected to theuntreated and/or treated contamination zone to further remove thetargeted contaminants.

REFERENCES

The following references, to the extent that they provide exemplaryprocedural or other details supplementary to those set forth herein, arespecifically incorporated herein by reference in their entirety asthough set forth herein in particular.

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C., Blaha, and Griffin, C. 1997. “Surfactant remediation field    demonstration using a vertical circulation well,” Ground Water.    35(6): 948-953.-   Knox, R. C., Shiau, B. J., Sabatini, D. A., and Harwell, J.    H., 1999. “Field demonstration studies of surfactant-enhanced    solubilization and mobilization at Hill Air Force Base, Utah,” in    Innovative Subsurface Remediation, Field Testing of Pysical,    Chemical, and Characterization Technologies, Brusseau, M. L.,    Sabatini, D. A., Gierke, J. S., Annable, M. D. (eds.), ACS symposium    series 725, 49-63, American Chemical Society, Washington D.C.-   Lipe, M., Sabatini, D. A., Hasegawa, M., and Harwell, J. H. 1996.    Ground Water Monitering and Remediation. 16(1): 85-92.-   Martel, R., Gelinas, P. J. and Desnoyyers, J. E., “Aquifer washing    by micellar solutions: 1 Optimization of alcohol-surfactant-solvent    solutions,” J. Contaminant Hydrology. 1998a. 29(4): 317.-   Martel, R., Rene, L, and Gelinas, P. 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1. A method for substantially removing subsurface contaminants,comprising the steps of: introducing an effective amount of at least onepre-selected surfactant solution; and introducing an effective amount ofat least one pre-selected biodegradable co-solvent, wherein theeffective amount of the at least one pre-selected biodegradableco-solvent in combination with the effective amount of the at least onepre-selected surfactant solution are capable of substantially removingsubsurface contaminants.
 2. The method of claim 1, wherein the effectiveamount of at least one pre-selected biodegradable co-solvent isintroduced first and the effective amount of the at least onepre-selected surfactant solution is introduced second.
 3. The method ofclaim 1, further comprising the step of: introducing a pre-selectedchemical oxidant to polish a final residual contaminant.
 4. The methodof claim 1 wherein the effective amount of at least one pre-selectedsurfactant solution is from about 0.05 weight % to about 15.0 weight %.5. The method of claim 1 wherein the effective amount of at least onepre-selected surfactant solution is from about 3.0 weight % to about 8.0weight %.
 6. The method of claim 1 wherein the effective amount of atleast one pre-selected surfactant solution is from about 1.0 weight % toabout 3.0 weight %.
 7. The method of claim 1 wherein the effectiveamount of at least one pre-selected surfactant solution is from about0.05 weight % to about 1.0 weight %.
 8. The method of claim 1 whereinthe at least one pre-selected surfactant solution is selected from thegroup consisting of an anionic surfactant, a cationic surfactant, anonionic surfactant or any combinations thereof and one or none of thecombinations thereof.
 9. The method of claim 2 wherein the amount of atleast one biodegradable co-solvent introduced before at least onesurfactant solution is about 0.02 pore volumes to about 0.5 porevolumes.
 10. The method of claim 3 wherein the effective amount of atleast one pre-selected chemical oxidant is selected from the groupconsisting of hydrogen peroxide, potassium permanganate and combinationsthereof.
 11. The method of claim 3 wherein at least one pre-selectedchemical oxidant is a free radical.
 12. A method for substantiallyexpediting subsurface remediation of contaminants comprising the stepsof: introducing at least one bio-degradable co-solvent first;introducing at least one surfactant solution capable of remediating atleast one subsurface contaminant; and introducing sequentially at leastone pre-selected chemical oxidant.
 13. The method of claim 12, wherein,in the step of introducing at least one bio-degradable co-solvent and atleast one surfactant solution capable of remediating at least onesubsurface contaminant and sequentially introducing at least onepre-selected chemical oxidant, the pre-selected chemical oxidant isintroduced by injecting.
 14. The method of claim 12, wherein at leastone subsurface contaminant is a dense non-aqueous phase liquid.
 15. Themethod of claim 12, wherein at least one subsurface contaminant is alight non-aqueous phase liquid.
 16. The method of claim 12, wherein atleast one bio-degradable co-solvent is selected from the groupconsisting of methyl esters of fatty acids, ethyl esters of fatty acids,and combinations thereof.
 17. The method of claim 12, wherein thesurfactant solution is a mixture of sodium dioctylsulfosuccinate andsodium dihexylsulfosuccinate.
 18. The method of claim 12, wherein thesurfactant solution is a mixture of sodium dioctylsulfosuccinate andpolyoxyethylene sorbitan monooleate.
 19. The method of claim 12, whereinthe surfactant solution is a mixture of sodium dioctylsulfosuccinate andlinear alkyl diphenyloxide disulfonate.
 20. The method of claim 12,wherein the surfactant solution is a mixture of alkylamine sodiumsulfonate and sodium dihexylsulfosuccinate.
 21. An abiotic process forpolishing at least one surfactant remediated subsurface contaminant inorder to further remediate at least one subsurface contaminant tosubstantially undetectable levels, comprising the step of: introducingan effective amount of at least one pre-selected chemical oxidantcapable of degrading the remaining at least one of subsurfacecontaminant to substantially undetectable levels.
 22. The process ofclaim 21, wherein the effective amount of at least one pre-selectedchemical oxidant is introduced by injection.
 23. The process of claim21, wherein at least one subsurface contaminant is a dense non-aqueousphase liquid.
 24. The process of claim 21, wherein at least onesubsurface contaminant is a light non-aqueous phase liquid.
 25. Theprocess of claim 21, wherein the effective amount of at least onepre-selected chemical oxidant is a free radical.
 26. The process ofclaim 21, wherein the effective amount of at least one pre-selectedchemical oxidant is selected from the group consisting of hydrogenperoxide, potassium permanganate, and combinations thereof.
 27. A methodfor substantially removing subsurface contaminants, comprising the stepsof: introducing an effective amount of at least one pre-selectedsurfactant solution, comprising the steps of: determining a contaminantsolubilization of a surfactant system; determining a surfactant sorptionand precipitation of the surfactant system; determining a surfactantnon-aqueous phase liquid behavior properties of the surfactant system toassess a potential for surfactant losses under subsurface conditions;and performing contaminant extraction-column studies to simulate flowthrough conditions in the aquifer; introducing an effective amount of atleast one pre-selected chemical oxidant, comprising the steps of:determining relative reaction rates of the reactant; determining thelife span of the reactant; evaluating the chemical demand associatedwith pH adjustment; and identifying geochemical characteristics of thesite; wherein the effective amount of at least one pre-selectedsurfactant in combination with the effective amount of at least onepre-selected chemical oxidant are capable of substantially removingsubsurface contaminants.
 28. The method of claim 27, wherein theeffective amount of a pre-selected biodegradable co-solvent isintroduced first and the effective amount of at least one pre-selectedsurfactant solution is introduced second, the pre-selected chemicaloxidant is then introduced to polish the final residual contaminant. 29.A method for determining chemical addition ratios and reaction times fora chemical oxidation system, comprising the steps of: determiningreaction kinetics; determining pH conditions; determining naturallyoccurring interference within the subsurface of the specific site; anddetermining mobility control of the injected oxidant to the targetedarea.
 30. A subsurface contaminant site substantially remediated by theprocess comprising the steps of: introducing an effective amount of atleast one pre-selected surfactant solution; and introducing an effectiveamount of at least one pre-selected chemical oxidant, wherein theeffective amount of at least one pre-selected surfactant in combinationwith the effective amount of at least one pre-selected chemical oxidantare capable of substantially removing subsurface contaminants.
 31. Thesubstantially remediated site of claim 30, wherein the effective amountof the pre-selected subsurface contaminant is introduced first and theeffective amount of at least one pre-selected chemical oxidant isintroduced second.
 32. The substantially remediated site of claim 30,wherein the pre-selected surfactant solution is selected from the groupconsisting of an anionic surfactant, a cationic surfactant, a nonionicsurfactant or any combinations thereof and one or more combinationsthereof.
 33. The substantially remediated site of claim 30, wherein thepre-selected surfactant solution is a mixture of sodiumdioctylsulfosuccinate and sodium dihexylsulfosuccinate.
 34. Thesubstantially remediated site of claim 30, wherein the pre-selectedsurfactant solution is a mixture of sodium dioctylsulfosuccinate andpolyoxyethylene sorbitan monooleate.
 35. The substantially remediatedsite of claim 30, wherein the pre-selected surfactant solution is amixture of sodium dioctylsulfosuccinate and linear alkyl diphenyloxidedisulfonate.
 36. The substantially remediated site of claim 30, whereinthe pre-selected surfactant solution is a mixture of alkylamine sodiumsulfonate and sodium dihexylsulfosuccinate.
 37. The substantiallyremediated site of claim 30, wherein at least one pre-selected chemicaloxidant is a free radical.
 38. The substantially remediated site ofclaim 30, wherein at least one pre-selected chemical oxidant is selectedfrom the group consisting of hydrogen peroxide, potassium permanganate,and combinations thereof.
 39. The substantially remediated site of claim30, wherein the effective amount of at least one pre-selected surfactantsolution is from about 0.05 weight % to about 15 weight %.
 40. Thesubstantially remediated site of claim 30, wherein the effective amountof at least one pre-selected surfactant solution is from about 3 weight% to about 8 weight %.
 41. The substantially remediated site of claim30, wherein the effective amount of at least one pre-selected surfactantsolution is from about 1 weight % to about 3 weight %.
 42. Thesubstantially remediated site of claim 30, wherein the effective amountof at least one pre-selected surfactant solution is from about 0.05weight % to about 1 weight %.
 43. The substantially remediated site ofclaim 30, wherein at least one pre-selected surfactant solution isanionic.
 44. The substantially remediated site of claim 30, wherein atleast one pre-selected surfactant solution is nonionic.
 45. A subsurfacecontaminant site substantially remediated by the process comprising thesteps of: introducing at least one surfactant solution capable ofremediating at least one subsurface contaminant; and sequentiallyintroducing at least one pre-selected chemical oxidant.
 46. Thesubstantially remediated site of claim 45, wherein the pre-selectedchemical oxidant is introduced by the method of injection.
 47. Thesubstantially remediated site of claim 45, wherein at least onesubsurface contaminant is a dense non-aqueous phase liquid.
 48. Thesubstantially remediated site of claim 45, wherein at least onesubsurface contaminant is a light non-aqueous phase liquid.